1. Field of the Invention
The present invention relates to a projector, and more particularly, to a cooling apparatus for projector casing for shielding the radiant heat.
2. Description of the Prior Art
In general, a projector usually uses a high power light bulb as the light source to provide a bright and clear image and offer a comfortable viewing environment for audiences, and thus turning the light bulb into the largest heat source of the projector. The temperature of the upper and lower casings adjacent to the light bulb is higher than the temperature at other parts of the casings. To assure the user""s safety and improve the product quality, prior-art projectors usually use fans to cool and reduce the temperature of the casing.
Please refer to FIG. 1 for a projecting light source 10 of a conventional projector, which comprises a light bulb 11 coupled to a lamp holder 13 by a movable fixture 12, and the lamp holder 13 being fixed to a lower casing 15, by a screw 14; wherein an upper casing 16 of the projector being disposed at a position as close as possible to the lamp 11 to minimize the thickness of the projector and meet the consumer""s requirements for a modern compact equipment. Therefore, although there is a cooling fan (not shown in the figure) on one side of the lamp 11, the lamp at its top has no shelter. Therefore, the upper casing 16 and the lamp holder 13 adjacent to the lamp 11 will still be heated up by the radiant heat and hot air produced by the high temperature of the lamp 11, and conducted through the lamp holder 13 to the lower casing 15 near the lamp holder 13, causing the temperature of the upper and lower casings of the projector near the light source 10 higher than the temperature of other parts of the casing. It does not only heat up the plastic casing to a high temperature, but also expedites the deterioration; even for metal casings, it will also produce heat of high temperature, which makes the use of projector unsafe and inconvenient.
In FIG. 2, it shows another light source 20 of a conventional projector, wherein a lamp 21 being coupled to a lamp holder 22; a lamp housing 23 being disposed inside the projector; the lamp holder 22 being placed and coupled into the lamp housing 23 from the bottom of the lamp housing through a slot (not shown in the figure) of the lower casing 25; and a fan 24 being disposed on one side of the lamp housing for cooling the lamp 21. Although a cover 231 not fully closed is disposed at the top of the lamp housing 23 for shielding the lamp 21 from directly lighting up the upper casing 26, the cover 231 of the lamp housing 23 closely attaches onto the upper casing 26 of the projector. Therefore, the radiant heat of the lamp 21 will still be conducted through the cover 231 and the lamp holder 22 to the upper and lower casings 25, 26. There is a gap between the cover 231 and the upper casing 26 due to the error of manufacturing or assembling, but it does not constitute an air duct for the airflow. The air in the gap remains still and is heated up continuously, which also ends up a high temperature it causes the temperature at the upper and lower casings adjacent to the light source 20 higher than other parts of the housing, and thus having the shortcoming of making the application of the projector unsafe and inconvenient.
The objective of the present invention is to provide a cooling apparatus for projector casing by using a sheet as a shielding for the radiant heat and facilitating the airflow to isolate the radiant heat and the hot air of high temperature near the lamp in order to reduce the temperature of the casing and improve the quality of the product.
To achieve the foregoing objective, the present invention comprises a lamp holder with a lamp inside a casing; at least one guiding surface at the lower edge proximate one side of the lamp holder; an ventilation outlet disposed on the lamp holder at a position corresponding to one side of the guiding surface proximate the casing; an upper sheet at the top of the lamp holder keeping a specific distance from the casing to define an upper air duct; a lower sheet at the bottom of the lamp holder keeping a specific distance from the casing to define a lower air duct and connecting to the guiding surface for installing a fan proximate one side of the guiding surface in order to blow the air through the lamp holder and the upper and lower air ducts and then discharge the hot air from the ventilation outlet for the heat dispersion.